Doing "age in bonds" is not as simple as it might seem from the phrase. John Bogle clarified his original recommendation by explaining that one should take into account the present value of pensions and Social Security, considering them as bonds, when doing the calculation. Around the same time, he mentioned that he thought typical Social Security had a value in the neighborhood of $300,000. Interest rates have dropped a lot since then, and using current interest rates, I calculated that $20,000 a year of Social Security payments for a couple was worth more like $600,000!! For most investors, doing the calculation the way John Bogle recommends results in all or most of their investment portfolio beings in stocks!!
Leaving the "age in bonds" guideline for the moment, the real answer to the question as to whether you're being too conservative lies in how you plan on spending the money. If you plan on using it for regular living expenses, keep in mind that even at a below historical average 2.5% inflation rate, you'll still need to increase your spending by 28% every ten years. To keep up, your investments should return at least 2.5% a year. That used to be easy enough with bonds or even, CDs, but that's not so easy any more. On this forum, there are lots of people who are worried about interest rates rising and bonds dropping in value, but there's also a contrary school, typified by the people at Credit Suisse, who believe that interest rates are likely to stay below inflation for the next 6-8 years and will never return to their past historical levels. Either scenario is bad news for someone withdrawing living expenses from a mostly bond portfolio.
Does this mean you should rush out and put 90% of your portfolio in stocks? Nope, particularly if you see yourself as likely to panic and sell at the bottom when the market drops. On the other hand, you might want to plan on a much lower withdrawal rate from your portfolio.